Mixers are used to mix and blend a variety of materials such as food products. Planetary mixers of this type are quite common and typically include a planetary gearing arrangement within the head of the mixer. In certain instances it may be desirable to utilize a food grade grease, which can provide less effective sealing against moisture entry than thicker, non-food grade grease. Regardless of the type of grease used, it is desirable to provide effective sealing within the mixer head to limit moisture reaching the bearings in the mixer head.